1 Thermally activated field-dependent magnetization reversal in bulk BiFe 0.5 Mn 0.5 O 3 D. Delmonte 1 *, F. Mezzadri 2 , C. Pernechele 1 , G. Calestani 2-3 , G. Spina 4 , M. Lantieri 5 , M. Solzi 1 , R. Cabassi 2 , F. Bolzoni 2 , A. Migliori 6 and E. Gilioli 2 1 Dipartimento di Fisica, Università di Parma, Parco Area delle Scienze 7/A, 43124 Parma, Italy 2 IMEM-CNR, Parco Area delle Scienze 37/A, 43124 Parma, Italy 3 Dipartimento di Chimica, GIAP Università di Parma, Parco Area delle Scienze 17/A 43124 Parma, Italy 4 Dipartimento di Fisica, Università di Firenze, via Sansone 1, 50019 Sesto Fiorentino (FI), Italy 5 Istituto Sistemi Complessi-CNR, via Madonna del Piano 10, 50019 Sesto Fiorentino (FI), Italy 6 IMM-CNR, via Gobetti 101, 40129 Bologna, Italy *Corresponding author E-mail: davide.delmonte@fis.unipr.it FAX: +39 0521 269206 TEL: +39 0521 269220 We report on the synthesis and characterization of BiFe 0.5 Mn 0.5 O 3 , a potential type-I multiferroic compound displaying temperature induced magnetization reversal. Bulk samples were obtained by means of solid state reaction carried out under the application of hydrostatic pressure at 6 GPa and 1100°C. The crystal structure is an highly distorted perovskite with no cation order on the B site, where, besides a complex scheme of tilt and rotations of the TM-O 6 octahedra, large off-centering of the bismuth ions is detected. Below T 1 = 420 K the compound undergoes a first weak ferromagnetic transition related to the ordering of iron rich clusters. At lower temperatures (just below RT) two distinct thermally activated mechanisms are superimposed, inducing at first an enhancement of the magnetization at T 2 = 288 K, then a spontaneous reversal centered at T 3 = 250 K, finally giving rise to a negative response. The application of fields higher than 1500 Oe suppresses the process, yielding a ferromagnetic like behaviour. The complementary use of SQuID magnetometry and Mössbauer spectroscopy allowed the interpretation of the overall magnetic behaviour in terms of an uncompensated weak competitive coupling between non-equivalent clusters of interactions characterized by different critical temperatures and resultant magnetizations. PACS numbers: 75.85.+t, 75.60.Jk, 76.80.+y, 75.30.Et, 75.30.Kz I. INTRODUCTION The BiFe 1-x Mn x O 3 solid solution is an interesting candidate to type-I multiferroism, poorly studied in its bulk form, 1,2,3 where complex magnetic properties are observed, as the so called magnetization reversal (MRV). MRV is the phenomenon for which the magnetic susceptibility changes its sign as the system is cooled,